This invention relates generally to reflective phase shifters, and more particularly, to high power digitally controlled reflective phase shifters.
In some phased array radars, a plurality of digitally controlled phase shifters are coupled to a corresponding plurality of antenna elements to produce a collimated and directed beam of radio frequency (RF) energy. One such digitally controlled reflective phase shifter selectively couples one of a number of impedances to a transmission line to provide that transmission line with one of a plurality of reflection coefficients and, hence, RF energy introduced into, and reflected from, the phase shifter is phase shifted an amount related to the one of a plurality of reflection coefficients provided by the selected impedance. Corresponding PIN diodes couple the impedances to the transmission line. Combinations of the different impedances yield different phase shifts, but power handling capacity of that phase shifter is limited to that of a single impedance component and the corresponding PIN diodes. Power handling capacity is thus limited to the power capacity of a single PIN diode. Therefore, for high power operation, the use of high power-high cost diodes, or the paralleling of many diodes to share power dissipation is required.